Ignition distributors

ABSTRACT

An ignition distributor for a road vehicle, including a casing and a driven shaft rotatably mounted within the casing, the driven shaft being adapted to be driven by the engine of the vehicle. A contact breaker assembly is mounted within the casing and a hollow cam shaft is mounted for limited angular movement of the driven shaft. The cam shaft is rotatable with the driven shaft to operate the contact breaker assembly, and the cam shaft is moved angularly relative to the driven shaft by a centrifugal mechanism to vary the ignition timing of the distributor. Interposed between the driven shaft and the cam shaft is a resilient member which damps angular movement of the cam shaft relative to the driven shaft while permitting the required angular movement of the cam shaft under the action of the centrifugal mechanism.

United States Patent [72] inventor William Harold Cooksey Walsall, England [21] Appl. No. 847,253 [22] Filed Aug. 4, 1969 [45] Patented Dec. 7, 1971 [73] Assignee Joseph Lucas (Industries) Limited Birmingham, England [32] Priority Aug. 22, 1968 [33] Great Britain 1 1 40,175/68 [54] IGNITION DISTRIBUTORS 1 Claim, 3 Drawing Figs.

[52] U.S. Cl.. 200/19 [51] Int. Cl H0111 19/00 [50] Field of Search ZOO/19,21,

[ 56] References Cited UNITED STATES PATENTS 2,473,343 6/1949 Du Rostu 64/25 2.823.374 3/1958 Redick 200/19 FOREIGN PATENTS 833,068 4/1960 Great Britain 200/19 Primary Examiner-D. F. Duggan Attorney-Holman & Stern rotatable with the driven shaft to operate the contact breaker assembly, and the cam shaft is moved angularly relative to the driven shaft by a centrifugal mechanism to vary the ignition timing of the distributor. interposed between the driven shaft and the cam shaft is a resilient member which damps angular movement of the cam shaft relative to the driven shaft while permitting the required angular movement of the cam shaft under the action of the centrifugal mechanism.

IGNITION DISTRIBUTORS BACKGROUND OF THE INVENTION This invention relates to ignition distributors of the kind including a casing, a driven shaft rotatably mounted within the casing and adapted to be driven by the engine of a road vehicle, a contact breaker assembly mounted within the casing, and a hollow cam shaft mounted for limited angular movement on said driven shaft, with the cam shaft being rotatable with said driven shaft to operate the contact breaker assembly and said cam shaft being moved angularly relative to said driven shaft by a centrifugal mechanism to vary the ignition timing of the distributor.

In distributors of the kind specified, unless the manufacturing tolerances of the centrifugal mechanism are rigidly controlled then in use noise can be generated by engagement of the parts of the centrifugal mechanism with one another as the cam shaft operates the contact breaker assembly. It is an object of the invention to provide a distributor wherein such noise generation is minimized.

SUMMARY OF THE INVENTION According to the invention, in a distributor of the kind specified a resilient strip is interposed between said driven shaft and said cam shaft with the end portions of the strip engaging the inner surface of the cam shaft at generally diametrically spaced points and the midregion of the strip being flexed to engage the circumference of a portion of reduced diameter of the driven shaft, so that the resilient strip moves with the cam shaft and bears against the portion of reduced diameter whereby friction between the portion of reduced diameter and the resilient strip damps angular oscillation of the cam shaft relative to the driven shaft. I

One example of the invention is illustrated in the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary, part sectional view of an ignition distributor,

FIG. 2 is a sectional view of the shaft assembly of the ignition distributor shown in FIG. I, and

FIG. 3 is a sectional view on the line 3-3 in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings, there is provided a distributor, driven shaft 11 which is journaled for rotation in a distributor casing 10. At its lower end, the shaft ll projects from the casing and is provided with a dog coupling through which the shaft I l is rotatably driven in timed relation to the crank shaft of an internal combustion engine with which the distributor is associated. Rotatably mounted on the upper end of the shaft I 1 within the casing 10 of the distributor, is a hollow cam shaft 12 which is held against axial movement relative to the shaft ll by means of a screw (not shown), the head of which engages a peripheral, internal, shoulder at the upper end of the cam shaft, and the shank of which is in screw threaded engagement with the shaft ll. The cam shaft 12 rotates with the shaft I1, and is coupled thereto through a conventional centrifugal advance mechanism, which, as the speed of rotation of the shaft 11 increases, displaces the cam shaft 12 angularly with respect to the shaft 11, while transmitting rotational movement of the shaft 11 to the cam shaft 12. The cam shaft 12 acts on a conventional contact breaker assembly 10a supported within the distributor casing 10, so that the contacts of the contact breaker assembly are opened and closed in timed relation to the rotation of the engine. The centrifugal advance mechanism varying the timing of the operation of the contact breaker assembly 10a as the speed of rotation of the engine varies.

It will be appreciated that owing to manufacturing tolerances and wear, free play can arise in the centrifugal mechanism. Moreover, as the cam follower of the contact breaker assembly rides on the cam shaft 12 then the cam shaft 12 is urged to reciprocate in an angular direction by the cam follower, as permitted by the free play in the centrifugal mechanism. As such angular reciprocation occurs, the moving parts of the centrifugal mechanism are moved into and out of engagement with one another and noise is generated.

In order to minimize the generation of noise in the centrifugal mechanism while allowing the necessary degree of movement of the cam shaft 12 under the action of the centrifugal mechanism, the shaft 11 is provided with a portion 13 of reduced diameter intermediate its ends, and resilient means is interposed between the shaft 11 and the cam shaft 12 to damp angular movements of the cam shaft 12 relative to the shaft 11. The resilient means is in the form of a strip 14 of spring steel the ends of which engage the inner surface of the cam shaft 12 at a pair of generally diametrically spaced points, and the midregion of which is flexed to engage the circumference of the portion 13 of the shaft 11. Thus the spring strip 14 moves with the cam shaft 12, and bears against the portion 13 of the shaft 11 so that friction between the portion 13 of the shaft 11, and the spring 14 damps angular oscillation of the cam shaft 12 relative to the shaft 11. The parameters of the arrangement are so chosen that although the cam shaft 12 is effectively damped, the function of the centrifugal mechanism is not materially effected.

I claim:

1. An ignition distributor comprising a casing, a driven shaft rotatably mounted within the casing and arranged to be driven.

in use by the engine of a road vehicle, a hollow cam shaft mounted for limited angular movement on said driven shaft, said cam shaft being rotatable with said driven shaft to operate a contact breaker assembly of the distributor, and said cam shaft being movable angularly relative to said driven shaft by a centrifugal mechanism housed within the distributor casing, to vary the ignition timing of the distributor, a resilient strip having opposite end portions and a midregion, said driven shaft being provided with a portion of reduced diameter, the opposite end portions of the resilient strip engaging the inner surface of the hollow cam shaft at a pair of generally diametrically spaced points and the midregion of the resilient strip being flexed for engaging the circumference of the portion of reduced diameter of the driven shaft so that the resilient strip moves with the cam shaft and bears against the portion of reduced diameter whereby friction between the portion of reduced diameter and the resilient strip damps angular oscillation of the cam shaft relative to the driven shaft.

IIK III k 

1. An ignition distributor comprising a casing, a driven shaft rotatably mounted within the casing and arranged to be driven in use by the engine of a road vehicle, a hollow cam shaft mounted for limited angular movement on said driven shaft, said cam shaft being rotatable with said driven shaft to operate a contact breaker assembly of the distributor, and said cam shaft being movable angularly relative to said driven shaft by a centrifugal mechanism housed within the distributor casing, to vary the ignition timing of the distributor, a resilient strip having opposite end portions and a midregion, said driven shaft being provided with a portion of reduced diameter, the opposite end portions of the resilient strip engaging the inner surface of the hollow cam shaft at a pair of generally diametrically spaced points and the midregion of the resilient strip being flexed for engaging the circumference of the portion of reduced diameter of the driven shaft so that the resilient strip moves with the cam shaft and bears against the portion of reduced diameter whereby friction between the portion of reduced diameter and the resilient strip damps angular oscillation of the cam shaft relative to the driven shaft. 